I think you should limit it to one Goddess per name. Persephone Hespera Juno is a clash of myths and one too many Goddess. I don't know if it bugs you, but I would not like my child to have two names in her name that weren't harmonious with each other, or were linked in a not so good way.

It’s great that you don’t mind the same syllable count for each part of the name and are unafraid of longer ones. How do you feel about same endings? For example, does having repeating –a endings bother you as in CosimaValentinaSeraphina D-? I’d rather have it different like sounds like CosimaDelphineBeatrice D-.

basicsand - Same endings don't bother me too much, but I think if all of the names in the combo have the same ending then it can be too much. For example Cosima Beatrice Alba sounds better than Cosima Seraphina Alba IMO. If than makes sense?